TW201503546A - Permanent magnet motor - Google Patents

Abstract

For a permanent magnet motor using a ferrite magnet, the present invention provides a permanent magnet motor which may maximize the torque generated by the permanent magnet and the torque generated by magnetic reluctance and also minimize the torque ripple factor while generating torque. The permanent magnet motor comprises: a permanent magnet rotor, which is a buried type permanent magnet rotor that the p-electrode of ferrite permanent magnet is received in laminated silicon steel plates; three U-shaped permanent magnets configured for one electrode and one outer periphery permanent magnet configured along the circumference of the outer periphery of the U-shaped permanent magnets to sequentially generate permanent magnet torque and generate reluctance torque for one electrode by two salient poles formed between the U-shaped permanent magnets and the outer periphery magnet and one center salient pole between U-shape permanent magnets of adjacent electrodes; and stators, which are composed of stator windings in winding distribution and M-phase and stator iron cores having laminates for receiving Ns slots of stator windings, wherein the ratio of Ns/M/P is a fraction. The permanent magnet motor is characterized in that the width of the center salient pole is set as <Tau>cp and the slot pitch of the stator iron core is set as <Tau>s, so that the width of center salient pole <Tau>cp is smaller than the slot pitch <Tau>s.

Description

Permanent magnet motor

The present invention is a permanent magnet motor structure in which a ferromagnetic magnet having a rectangular parallelepiped shape is used, and a permanent magnet motor mainly composed of a reluctance torque is used as a target, and a low torque is chopped and a large twist can be generated.

In the permanent magnet motor that generates a large torque, a so-called surface magnet type motor structure in which a magnet is placed on the surface of the rotor by using a high-performance neodymium magnet is practically used, and high torque and low torque can be achieved. Permanent magnet motor on both sides of the wave. However, in recent years, as the price of neodymium magnets has risen and is difficult to obtain, research and development of permanent magnet motors using ferrite magnets have tended to progress. The price of the ferrite magnet is less than 1/10 of that of the neodymium magnet, which is relatively inexpensive, but the residual magnetic flux density and the low holding power are both 1/3 or less of the neodymium magnet. Therefore, in the permanent magnet motor using the ferrite magnet, in order to approximate the torque generated by the neodymium magnet motor, it is necessary to use the reluctance torque in addition to the permanent magnet torque. It is a structure in which a permanent magnet is embedded in a rotor core.

The development of a permanent magnet motor using a ferrite magnet has the following points.

(1) In order to ensure the maximum torque, the surface area of the permanent magnet occupied by one pole is increased to maximize the torque generated by the permanent magnet.

(2) A structure in which the reluctance torque can be fully utilized.

(3) Since the holding force of the permanent magnet is 1/3 low, the thickness of the permanent magnet is ensured so as not to demagnetize when the stator winding flows a current.

(4) The use of reluctance torque is due to the fact that the harmonic magnetic flux passing through the core is increased, so it is conceivable that the torque ripple is increased. In particular, there are torque ripples that reduce the maximum current energization and maximum torque.

In the disclosed example, Patent Document 1 discloses a permanent magnet motor in which a permanent magnet is embedded in a rotor core and a permanent magnet torque and a reluctance torque are utilized.

Here, FIG. 7 of Patent Document 1 discloses a configuration in which a permanent magnet is embedded in a rotor core, and the subject matter is closest to the configuration of the present invention. Hereinafter, the features and problems will be described with reference to FIGS. 9 and 10 .

The permanent magnets are arranged in four poles, and the one-pole permanent magnets are composed of four rectangular parallelepiped permanent magnets 61-64. Among them, one permanent magnet 64 has a configuration in which the outer circumference of the rotor of the d-axis is circumferentially long, and the remaining three permanent magnets 61, 62, and 63 are arranged in a U shape as shown. Patent Document 1 is an invention for improving the characteristics of a permanent magnet in a part of a reluctance motor, and the reluctance torque is a central protrusion between permanent magnets arranged in a U-shape corresponding to a position corresponding to the q-axis. The composition of the pole 74.

In general, both reluctance torque and permanent torque are generated. The torque formula of the permanent magnet motor is as shown in Equation 1.

τ=p[keiq+(Ld-Lq)idiq] (Equation 1)

Here, p: pole logarithm, ke: power generation constant, Ld: d-axis inductance, Lq: q-axis inductance, id: d-axis current, iq: q-axis current

In the above formula, the first term is a torque component formed by a permanent magnet, and the second term is a reluctance torque component. Here, the torque formed by the permanent magnet of the first item is proportional to the power generation constant ke. The power generation constant ke is slightly proportional to the residual magnetic flux density Br of the permanent magnet and the area Am of the permanent magnet.

In addition, the reluctance torque is proportional to (Ld-Lq).

Ld is proportional to the magnetic flux amount Φd when a constant current flows through the d-axis, and Lq is proportional to the magnetic flux amount Φq when a constant current flows through the q-axis.

Patent Document 1 discloses a structure in which the permanent magnet formed by the arrangement of four permanent magnets 61-64 and the reluctance torque formed by the center salient pole 74 can be used in combination. The torque generated by the permanent magnet is proportional to the residual magnetic flux density and area of the permanent magnets 61, 62, 63 in which the permanent magnets are arranged in a U shape, and the residual of the permanent magnet 64 constituting the magnetic circuit connected in series thereto is added. Produced by magnetic flux density and area.

In addition, when the reluctance torque is described, the d-axis magnetic circuit is permanently magnetized in the case of the d-axis energization current Id shown in FIG. The magnetic permeability of iron is as small as 1, and the thickness of the magnet is thicker than the gap between the stator and the rotor. Therefore, the permanent magnet 64 is used as the first magnet, the magnetic resistance of the permanent magnets 61, 62, and 63 is increased, and the d-axis magnetic flux Φd1 is small. Therefore, the d-axis inductance Ld which is proportional to the d-axis magnetic flux Φd1 becomes small.

Further, in the case of the q-axis current Iq shown in FIG. 9, the magnetic circuit of the q-axis has a magnetic permeability of 1000 or more due to the magnetic pole of the magnetic pole 74, so that the magnetic resistance can be made small, and the magnetic flux Φq of the q-axis can be made large. . Therefore, the q-axis inductance Lq which is proportional to the q-axis magnetic flux Φq also becomes large. In the above principle, (Ld-Lq) can be made larger (although the sign is reversed, since Id holds a negative sign, it becomes +), and a large reluctance torque can be generated. According to the above theory, Patent Document 1 discloses a permanent magnet motor that can simultaneously generate permanent magnet torque and reluctance torque.

Further, Patent Document 2 discloses a permanent magnet motor configuration in which a so-called buried rotor structure is used to reduce cogging torque by utilizing a magnetic torque. Patent Document 2 discloses that the number of grooves Ns of the stator is divided by the number of poles P of the permanent magnets and the number of phases M, Ns/p/m, which is a fraction, and the so-called fractional groove constitutes a permanent magnet motor, in particular, It is possible to reduce the width of the permanent magnet of the cogging effect when the current is not energized.

[Previous Technical Literature] [Patent Literature]

[Reference 1] Japanese Patent Laid-Open No. 3290392

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-70192

As described above, in Patent Document 1, the reluctance torque is utilized by disposing four permanent magnets between the salient pole and the salient pole which are the center, and the width of the center salient pole is larger than the width of the trench of the stator. And the composition of the permanent magnet torque. However, the structure for compensating for the disadvantage of the low residual magnetic flux of the ferrite magnet is to sufficiently enlarge the surface area of the permanent magnet, thereby making it possible to form a permanent magnet motor that is slightly closer to the torque generated by the conventional neodymium magnet motor. .

In Patent Document 1, since the permanent magnet used is a single neodymium magnet or a neodymium magnet and a ferrite and a bonded magnet, the residual magnetic flux density is large. Therefore, in order to make the first item of the above formula 1 The permanent magnet torque becomes large, and it is not necessary to maximize the permanent magnet area. Further, in order to improve the reluctance torque, the width of the center salient pole 74 is made larger than the pitch of the stator trenches. According to this, in order to achieve the purpose of the automatic vehicle drive motor, the characteristic that the maximum output can be maintained in the high speed field is realized.

However, in the case of using a ferrite magnet having a low residual magnetic flux density, a structure for maximizing the permanent magnet torque, that is, a structure for increasing the area of the permanent magnet is not disclosed. Further, in the configuration of the center salient pole 74 shown in Patent Document 1, it is difficult to maximize the area of the permanent magnet, and there is a problem that the permanent magnet torque cannot be sufficiently increased.

Furthermore, for the reluctance torque, in the permanent magnet motor that generates a large torque, the q-axis current circuit Iq, the q-axis magnetic circuit Due to the magnetic saturation on the stator side, the magnetic flux Φq1 of the q-axis does not necessarily become large. Therefore, it is also impossible to increase Lq. Further, with respect to the magnetic circuit of the d-axis, the magnetic flux Φd1 can be made small by the above theory, but since the width of the central salient pole 74 is large, the magnetic flux Φd2 which crosses the central salient pole 74 in the d-axis direction as shown in Fig. 9 is generated. . The magnetic permeability of the iron constituting the center salient pole 74 in the magnetic circuit of Φd2 is as large as 1000 or more, and the magnetic flux is small in the gap length of the magnetic circuit because the gap between the stator and the rotor is short, whereby the magnetic flux Φd of the d-axis becomes large. Therefore, it is not always possible to increase the absolute value of (Ld - Lq), and there is a problem in maximizing the magnetic resistance.

In addition, in order to obtain the above-described large reluctance torque, the d-axis magnetic flux Φd2 which is an inverse effect also causes the pulsation torque, and the low torque chopping when the maximum torque is generated becomes a problem.

In addition, in any of the above-mentioned Patent Documents 1 and 2, the configuration in which the torque ripple of the permanent magnet is reduced in a state where the reluctance torque is generated by the winding current of the permanent magnet motor is not disclosed.

The present invention provides a permanent magnet motor that overcomes the disadvantages of the conventional permanent magnet motor described above and uses a ferrite magnet, and provides torque and reluctance torque generated by the permanent magnet to be maximized and allows current to flow. The torque ripple becomes the smallest permanent magnet.

The permanent magnet of the first aspect of the invention is a permanent magnet rotor which is a P-embedded permanent magnet rotor in which a ferrite permanent magnet is housed in a laminated tantalum steel sheet, and is configured to have three poles arranged in one pole. The U-shaped permanent magnet and the one outer peripheral permanent magnet which are disposed in the circumferential direction of the outer peripheral portion of the U-shaped permanent magnet generate permanent magnet torque, and are formed on the first pole by The two salient poles between the U-shaped permanent magnet and the outer peripheral magnet and the one central salient pole formed between the U-shaped permanent magnets adjacent to each other generate a reluctance torque; and a stator A stator core of a distributed winding and an M phase, and a stator core having a stack of Ns slots accommodating the stator winding, and the ratio of the Ns/M/P is a fraction, and the permanent The magnet motor is characterized in that when the width of the center salient pole is τcp and the groove pitch of the stator core is τs, the width τcp of the center salient pole is made smaller than the groove pitch τs.

According to a second aspect of the invention, in the permanent magnet motor of the first aspect of the invention, the width of the two salient poles formed between the U-shaped permanent magnet and the outer peripheral permanent magnet is set to When τbp, the width of τbp is made smaller than the groove pitch τs.

In the permanent magnet motor according to the second aspect of the invention, the width τcp of the center salient pole is set to 0.1 < τcp / τs < 1.0 with respect to the groove pitch τs.

In the permanent magnet motor according to the third aspect of the invention, the width τcp of the center salient pole is set to 0.35 < τcp / τs < 0.7.

The invention of the fifth application patent scope is as follows: In the permanent magnet motor according to the second aspect, the total width τap of the width τbp of the salient pole formed between the U-shaped permanent magnet and the outer peripheral permanent magnet and the width τcp of the center salient pole is included for one pole. For the groove pitch τs, it is set to 2.1 < τap / τs < 3.35.

The invention of claim 6 is as follows: in the permanent magnet motor described in claim 5, it is assumed that 2.57 < τap / τs < 2.84.

According to the invention of claim 1, the permanent magnet torque and the magnetic force can be made by setting the width τcp of the center salient pole to be smaller than the groove pitch τs and generating the maximum torque when the maximum current is energized. The sum of the resistance torques becomes maximum and the ripple of the torque is reduced.

According to the invention of claim 2, by setting the width of τbp and τcp to be smaller than the groove τs, the sum of the permanent magnet and the reluctance torque at the time of maximum current energization can be maximized, and the rotation is made. The chopping rate of the moment is minimized.

According to the invention of claim 3, the groove pitch τs of the stator core is set to 0.1 < τcp by the width τcp of the center salient pole formed between the U-shaped permanent magnets adjacent to each other. /τs<1.0, which maximizes the sum of the permanent magnet and the reluctance torque when the maximum current is energized, and reduces the chopping rate of the torque.

By applying for the invention of the fourth scope of the patent, by When the width of the center salient pole formed between the U-shaped permanent magnets adjacent to each other is τcp, the value of the width τcp of the center salient pole to the groove pitch τs is set to 0.35 < τcp / τs < 0.7. The sum of the reluctance torques can be maximized and the torque ripple can be reduced.

According to the invention of claim 5, the U-shaped permanent magnet and the permanent magnet which is disposed on the outer peripheral portion of the U-shaped permanent magnet and which is long in the circumferential direction are included for one pole. The width τ bp between the width of the salient pole and the width τ ap of the width τ cp of the central salient pole formed between the adjacent U pole permanent magnets is set to 2.1 < τap / τs < 3.35 with respect to the groove τs. It can maximize the sum of the permanent magnet and the reluctance torque when the maximum current is energized, and reduce the torque ripple.

By applying the invention of the sixth paragraph of the patent scope, by setting τap to τs to 2.57<τap/τs<2.84, the sum of the permanent iron and the reluctance torque at the time of maximum current circulation can be maximized, and Reduce torque ripple.

1‧‧‧ permanent magnet motor

2‧‧‧stator

3‧‧‧Rotor

4‧‧‧ Stator core

41‧‧‧ trench

42‧‧‧ Stator teeth

43‧‧‧Standard core back

5‧‧‧statar winding (stator winding)

6‧‧‧ permanent magnet

61, 62, 63, 64‧‧‧ permanent magnets

61, 62, 63‧‧‧U-shaped permanent magnets

64‧‧‧Peripheral permanent magnet

7‧‧‧Rotor core

71, 72‧‧‧

73‧‧‧Rotor magnetic circuit

74‧‧‧ center sharp

75‧‧‧Magnetic pole piece

8‧‧‧Rotary axis

9‧‧‧Voids

10‧‧‧ Magnet holding member

11‧‧‧Static pin

12‧‧‧End bracket

13‧‧‧End board

14‧‧‧ position detector

14A‧‧‧ Stator of position detector

14B‧‧‧Rotor of position detector

15‧‧‧ bearing

Τs‧‧‧ trench spacing

Τcp‧‧‧ center width

Τbp‧‧‧ is the width of two salient poles formed between the U-shaped permanent magnet and the peripheral permanent magnet

Τap‧‧‧ contains the total width of the width τbp of the salient pole and the width τcp of the adjacent central salient pole

Fig. 1 is a cross-sectional view showing an essential part of a permanent magnet motor according to an embodiment of the present invention.

Fig. 2 is a view showing the overall configuration of a permanent magnet motor according to an embodiment of the present invention.

Fig. 3 is a cross-sectional view showing the direction of the permanent magnet motor in the axial direction according to the embodiment of the present invention.

Fig. 4 is a schematic view showing the operation of the permanent magnet motor of the present invention.

Fig. 5 is a schematic view showing the operation of the permanent magnet motor of the present invention.

Fig. 6 is a characteristic diagram showing torque chopping and torque with respect to the center salient pole τcp and the groove pitch τs of the permanent magnet motor according to the embodiment of the present invention.

Fig. 7 is a characteristic diagram showing torque ripple and torque with respect to the center salient pole τcp and the groove pitch τs of the permanent magnet motor according to the embodiment of the present invention.

Fig. 8 is a characteristic diagram showing the cogging torque of the ratio τcp/τs of the center salient pole τcp and the groove pitch τs of the permanent magnet motor according to the embodiment of the present invention.

Fig. 9 is a schematic view showing the operation of the permanent magnet motor of the prior art.

Fig. 10 is a schematic view showing the operation of the permanent magnet motor of the prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Example)

Figure 1 shows the weight of a permanent magnet motor in accordance with an embodiment of the present invention. The profile of the part.

Fig. 2 is a view showing the overall configuration of a permanent magnet motor according to an embodiment of the present invention.

Figure 3 is a cross-sectional view showing the direction of the permanent magnet motor in the axial direction according to an embodiment of the present invention.

Figure 1 is an enlarged view of the 2-pole portion of Figure 2. In the figure, only the numerical part indicates the part, and the bottom line below the number indicates the assembly of the parts.

In the figure, the permanent magnet motor 1 is composed of a stator (fixed body) 2 and a rotor (permanent magnet rotor) 3. The stator 2 is mainly composed of a stator core 4 and a stator winding 5. Further, the rotor 3 is composed of a permanent magnet 6 and a rotor core 7 of a laminated tantalum steel plate, a rotating shaft 8 and a magnet holding member 10 for suppressing the movement of the permanent magnet in the axial direction. Here, the stator 2 is configured to be fixed to the end plates 13 at both axial ends by the stator pins 11 and the end brackets 12 penetrating the stator core 4.

The rotor 3 is rotatably supported by the end plate 13 via a bearing 15. Further, the stator 14A of the position detector for detecting the position of the rotor 3 is fixed to the end plate 13, and the rotor 14B of the position detector is fixed to the shaft of the rotary shaft 8, thereby constituting the position detector 14. Here, the position detector 14 is shown by taking a resolver as an example.

A groove 41 for accommodating the stator winding 5 is provided on the inner circumference of the stator core 4. In the figure, the stator core 4 is composed of, for example, an electromagnetic laminated 矽 steel plate having a thickness of 0.5 mm, and has a peripheral shape as shown in the figure, and is composed of a stator pin. The hole for use of the hole 11 or the groove 41 of the stator winding 5, the stator tooth portion 42 of the magnetic circuit constituting the permanent magnet 6 of the rotor 3, and the stator core back portion 43 are formed. In addition to this, the cooling fan can be integrally formed in the outer peripheral portion as needed. The stator core 4 is a laminated member, but the outer peripheral portion thereof may be welded as needed to increase the mechanical strength.

In the embodiment of the present invention, there is a stator composed of a distributed winding and an M-phase stator winding 5, and a stator core holding a stack of Ns grooves accommodating the stator winding, and a P-pole rotor, and Ns/M/P is a permanent magnet motor that is composed of fractions.

Here, the ratio of the number of rotor poles P to the number of stator slots Ns is explained by an embodiment of a permanent magnet motor having a 2:9 configuration. Therefore, the width τs (groove pitch) of the circumferential direction of one groove is represented by the range shown in the figure, and since the number of grooves per one pole (electric angle of 180 degrees) is 4.5, the electrical angle is 40 degrees. Further, as shown in Fig. 1, the distance between the grooves 41 and the stator tooth portion 42 is the same as "τs". In FIGS. 4 and 5, the distance between the stator tooth portions 42 is indicated by "τs".

The number of grooves Ns of the stator core is represented by an example of 36, and the number of poles P of the rotor 3 is represented by an example of eight poles. Further, the number M of the stator windings 5 of the permanent magnet 1 is set to 3 which is generally widely used. That is, the number of grooves per phase per pole Nspp=Ns/P/M is 3/2, which is a non-integer and is a fractional groove. Therefore, the number of grooves 36 of the stator 2 and the number of poles 8 of the rotor are a structure in which the groove number of the so-called groove number 9 and the number of poles of the rotor 2 is repeated four times in the circumferential direction.

Hereinafter, the permanent object which is the object of the embodiment of the present invention will be described. The rotor of the magnet motor is constructed. The rotor 3 is composed of a permanent magnet 6 and a rotor core 7 to constitute a magnetic circuit. The permanent magnet 6 is a rectangular parallelepiped ferrite magnet which is easy to manufacture and low in price. Further, the rotor core is made of a laminated tantalum steel sheet in the same manner as the stator core 4.

In the case of a permanent magnet of one pole, three rectangular ferrite magnets 61, 62, and 63 embedded in a U-shape as shown in the figure are stacked in the U shape. The rectangular parallelepiped having a long circumferential direction on the outer peripheral side of the rotor of the permanent magnet is composed of four outer peripheral permanent magnets 64 composed of ferrite.

Accordingly, the salient poles 71, 72 and the central salient poles 74 are formed on the surface of the rotor, and the salient poles 71, 72 are formed in the U-shaped permanent magnets (61, 62, 63) and the rotors disposed in the U-shaped permanent magnets. Between the outer peripheral permanent magnets 64 having a long circumferential direction on the outer peripheral side, the central salient poles 74 are formed between U-shaped permanent magnets adjacent to each other.

With this configuration, the magnetic circuit of the permanent magnet forms a magnetic circuit that leads from the three permanent magnets 61, 62, 63 to the stator via the salient poles 71, 72, and a magnetic circuit that leads to the stator via the outer peripheral permanent magnet 64. Two.

The permanent magnet motor 1 according to the embodiment of the present invention is characterized in that the width of the center salient pole 74 between the U-shaped permanent magnets to be formed adjacent to each other is set to τcp, and the stator core 4 is set. When the distance between the grooves 42 is τs, τcp is smaller than τs (τcp < τs). Further, the permanent magnet 62 that forms one portion of the U-shaped magnet disposed on the inner diameter side is disposed to have a larger inner diameter than the permanent magnets 61 and 63 disposed in the radial direction. The side is characterized.

An operational principle diagram showing the effects of the embodiment of the present invention is shown in Figs. 4 and 5 . Fig. 4 shows a magnetic circuit of the d-axis, and Fig. 5 shows a magnetic circuit of the q-axis. Here, in order to clarify the difference between the conventional example and the embodiment of the present invention, it is represented by the same four-pole configuration as the conventional example.

According to the configuration of the embodiment of the present invention, by setting the width τcp of the center salient pole to be small, the permanent magnets 61 and 63 arranged in the radial direction of the U-shaped permanent magnet are disposed on the more central salient pole 74. The permanent magnet 62 can be disposed closer to the inner diameter, and the length of the permanent magnets 61, 63 in the radial direction can be increased. With the above configuration, the total surface area of the three permanent magnets 61, 62, 63 can be increased. Since the power generation constant Ke increases in proportion to the residual magnetic flux density Br of the permanent magnet and the area Am of the permanent magnet as described above, the permanent magnet torque shown in Formula 1 can be increased. Accordingly, the effect of reducing the torque caused by the low residual magnetic flux density of the ferrite magnet with respect to the neodymium magnet increases.

When the reluctance torque is described, the d-axis energizing current Id shown in FIG. 4 is the same as the conventional example of FIG. 9, and the d-axis magnetic circuit has a magnetic permeability as small as 1 due to the permanent magnet. Since the gap is thicker, the permanent magnets 64 are included, the magnetic resistance of the permanent magnets 61, 62, and 63 is increased, and the d-axis magnetic flux Φd1 is small. Therefore, the d-axis inductance Ld which is proportional to the d-axis magnetic flux Φd1 also becomes small.

Further, in the conventional example of Fig. 9, the magnetic flux Φd2 which is transverse to the central salient pole 74 in the d-axis direction, in the embodiment of the present invention, reduces the area of the magnetic circuit by narrowing the width τcp of the central salient pole 74, The magnetic resistance is small. Therefore, as in the conventional example, there is an advantage that the d-axis inductance Ld is not increased. This reduces the overall d-axis inductance. Reducing the magnetic flux Φd2 having an inverse effect on the reluctance torque increases the reluctance torque and also reduces the main cause of torque ripple which is a problem in the permanent magnet motor generated by the reluctance torque. Accordingly, low torque ripple can be achieved.

As shown in FIG. 5, when the current Iq is applied to the q-axis, the magnetic circuit of the q-axis has a magnetic permeability of 1000 or more due to the magnetic permeability of the magnetic pole 74, so that the magnetic resistance can be made small. The magnetic flux Φq of the q-axis is made larger. Therefore, the q-axis inductance Lq which is proportional to the q-axis magnetic flux Φq also becomes large.

Since the width τcp of the center salient pole 74 is narrow, the magnetic flux Φq1 becomes small, and the magnetic flux Φq2 flowing between the salient poles 71 and 72 complements the portion thereof, so that the inductance Lq of the q-axis does not become small. Therefore, as a whole, the absolute value of (Ld-Lq) becomes large, and the reluctance torque is increased to reduce the effect of chopping. The q-axis magnetic flux (Φq1, Φq2) balances the magnetic circuit between the center salient pole 74 and the salient poles 71 and 72, and the partial saturation in the rotor disappears, so that torque increase and low torque ripple can be achieved.

The torque generated by the permanent magnet is used, and the torque of the permanent magnet motor of the reluctance torque is described in the above formula 1. However, by the configuration of the embodiment of the present invention described above, the surface area of the permanent magnet can be increased. Since the power generation constant ke is increased, there is an effect of increasing the permanent magnet torque of the first term of Equation 1. In addition, according to the above configuration, the inductance Lq of the q-axis such as saturation does not necessarily increase, but the inductance Ld of the d-axis is permanently long in the circumferential direction of the peripheral portion of the U-shaped permanent magnet. The division of the magnetic circuit generated by the magnet 64 and the reduction of the magnetic flux Φd2 by the shortening of the center salient pole width τcp can be reduced, whereby the reluctance torque can be increased.

Further, when the width τbp of the two salient poles 71, 72 is increased, a magnetic flux which is generated by the magnetic flux Φd2 by the magnetic flux re-rotation of the stator winding is generated, which has an inverse effect on the torque. In the embodiment of the present invention, the effect of increasing the reluctance torque is also obtained by the width τbp being smaller than the groove pitch τs of the stator core.

As described above, the width τbp of the formed salient poles 71 and 72 and the width τcp of the center salient pole 74 are smaller than the groove pitch τs, and the magnetic flux circulating in the rotor can be reduced when the current flows through the stator winding. . In addition to the above-described increase in torque and reduction in torque chopping, there is also the effect of reducing the leakage inductance of the stator winding and the force rate of the permanent magnet motor. The boost rate can help reduce power supply capacitance and boost output.

Returning to Fig. 1 and Fig. 2, in the rotor configuration of the embodiment of the present invention, in addition to the configuration described above, a short-circuit prevention gap 9 is formed at both ends of each permanent magnet of the rotor as shown, or a magnetic body constituting the rotor. The rotor magnetic circuit 73 of the road and the pole piece 75 (the magnetic pole between the permanent magnet 64 and the outer circumference of the rotor). Further, the rotor magnetic circuit 73 and the rotor core on the inner circumference side, or between the salient poles 71 and 74 or between 72 and 74 constitute a bridge portion which is connected by a thin 矽 steel plate.

In Fig. 1, the winding arrangement of 9-channel and 2-pole is shown. Here, U, V, and W represent windings belonging to the respective phases. here, The additional + mark indicates the direction in which current flows from the back side of the paper to the surface, and the - mark indicates the opposite winding direction. The 9 groove portions shown in the figure are repeatedly arranged three times in the groove (not shown), and these may be connected in series to be driven by one inverter. In the large output motor, a 3-phase winding of 9 slots is driven by one inverter, and the rest is driven by the other three inverters.

The advantages of the above-described two-pole and nine-divided fractional grooves are shown below.

Since the phases of the rotors of the stator windings belonging to one phase are different from each other with respect to the poles, there is an advantage that the value of the winding coefficient with respect to the fundamental wave does not decrease too much, and the influence of the high harmonics can be effectively reduced. This provides a permanent magnet motor with less torque ripple for the motor. In the configuration of a permanent magnet motor in which the reluctance torque of the embodiment of the present invention is mostly employed, the above-described advantages of the fractional groove are an indispensable technique for reducing the torque ripple caused by the use of the reluctance torque. . By using fractional grooves, torque ripple can be reduced to a practical level. Accordingly, it is not necessary to adopt a configuration for reducing the skew of the torque ripple, and the number of manufacturing steps can be reduced. Furthermore, there is an advantage that the torque can be increased compared to a motor that is biased by an integer groove.

In addition, the combination of the above-mentioned number of poles and the number of grooves, as described above, for the permanent magnet motor in which the reluctance torque is used, there is also a possibility of reducing the increase in torque chopping, but a general integer groove which becomes an integer with respect to Nspp. In the different parts of the winding configuration, it is necessary to consider reducing the torque ripple formed by the magnetomotive force of the windings of different high harmonics.

In the above configuration, the maximum torque is 4kNm and the maximum is used. A simulation analysis of the torque and torque chopping of the permanent magnet motor of the rectangular ferrite magnet of the embodiment of the present invention, which is of the 120 kW class and the outer shape Φ400 and the stator core length of 400 mm, is output.

As a result, FIG. 6 shows the torque chopping tpp and the torque tav with respect to the ratio of the center salient pole width τcp of the permanent magnet motor and the groove pitch τs.

Fig. 7 shows torque chopping tpp and torque tav with respect to the ratio of the salient pole width τap of the permanent magnet motor to the groove pitch τs.

Fig. 8 shows the cogging torque tcog with respect to the ratio τcp/τs of the center salient pole width τcp of the permanent magnet and the groove pitch τs. In Fig. 8, the torque tav of one of the vertical axes is divided by the value which is the largest in the analysis so as to be dimensionless. The torque chopping tpp of the other of the vertical axes is expressed as % by dividing the difference between the maximum and minimum of the torque chopping by the average value of the torque. The cogging torque tcog is also expressed in terms of the ratio with respect to the maximum.

The ampere contactor (the product of the winding and the current per unit circumferential length of the gap surface) of the motor design in the gap portion of the analysis object is 1500 A/cm when the maximum current (maximum torque) is reached, and the torque/volume is equivalent. A permanent magnet motor produced with a large torque of 100 Nm/l (liter).

When designing the motor, various parameters are considered to affect the torque and torque ripple. In the embodiment of the present invention, in particular, in a permanent magnet motor using a ferrite magnet having a low magnetic flux density and having to sufficiently utilize a reluctance torque, the center salient pole width τcp causes a large torque and torque ripple. influences. Fig. 6 shows torque ripple and torque with respect to the ratio of the center salient pole width τcp of the permanent magnet motor to the groove pitch τs. Relative to Figure 6 The change of the torque chopping of τcp/τs, as shown in the figure, shows the result of the torque increase by reducing τcp/τs, and proves that the principle of the embodiment of the present invention shown in Figs. 4 and 5 is correct.

In Fig. 6, the conventional example shows that τcp/τs is 1.5, and in the embodiment of the present invention, by setting τcp/τs to 1 or less, the torque tav can be greatly improved. Further, it has been found that the groove pitch τs of the stator core by the width τcp of the center salient pole formed between the U-shaped magnets adjacent to each other is selected to be 0.1<τcp/τs<1.0, and a large turn can be simultaneously achieved. Moment and low torque chopping.

Further, in FIG. 6, as for the torque chopping tpp, it has been found that the torque ripple can be suppressed to 10% or less, and the large torque tav can be obtained, in particular, by setting τcp/τs to a range of 0.35 to 0.7.

In this way, in the embodiment of the present invention, by reducing the width τcp of the central salient pole 74, large torque and low torque chopping can be simultaneously achieved.

Next, attention is paid to the center salient pole τcp, and the U-shaped magnets 61, 62, 63 formed at the principal angles for generating the reluctance torque, and the outer peripheral permanent magnets 64 disposed in the outer peripheral portion thereof in the circumferential direction. The total salient pole width τap formed by the salient poles 71 and 72 between the salient poles 71 and 72 and the U-shaped magnets 61 and 63 formed between the adjacent poles causes a large torque and torque ripple. influences.

The above analysis is actually calculated by changing the circumferential length of the rotor of the permanent magnet 64. As a result, it can be seen that there is a range in which τap/τs can increase the optimum τap/τs of the average torque tav. Furthermore, It is known that there is a point at which the torque chopping is the smallest at a point different from the τap/τs giving the maximum average torque described above.

As shown in Fig. 7, τap/τs where the average torque tav becomes large is 2.1 < τap / τs < 3.35. The torque in which the average torque tav is higher than the average torque appearing in the interval of τcp/τs in Fig. 6 can be generated in this interval. Further, as a result of the analysis of FIG. 7, it is understood that torque ripple is minimized particularly in the point where τap/τs is 2.74. Here, the minimum torque ripple can be reduced to 7%. Practically, the torque ripple is 10% or less. In order to ensure torque ripple of 10%, the condition that 2.77 < τap / τs < 2.84 is centered on the above 2.74 is the optimum range.

In each of the above regions, the point at which the maximum torque is generated and the point at which the torque ripple is minimized are slightly different, but in this range, the sensitivity with respect to the torque is relatively low, and the torque ripple can be minimized. The range is specified as the optimum range of motor characteristics.

In the permanent magnet type reluctance motor which is the object of the embodiment of the present invention, the width of the magnet (the outer peripheral width of the rotor of the pole piece 75) / the pitch of the magnetic poles have an optimum value, and the width and reluctance of the magnet are measured from the viewpoint of the output torque. The balance of the magnetic pole width is better, that is, it can be maximized. That is, when the magnet is increased, the magnet torque is increased, but the reluctance torque is decreased. When the magnet is reduced, the magnet torque is increased, but the reluctance torque is increased. Although this has nothing to do with the groove pitch, the selection of τcp/τs is the selection of the magnet width/pole pitch for giving the maximum torque.

The above result range is that the width τbp of the salient poles 71, 72 is smaller than the range of the groove pitch τs of the stator core, and is generated by the magnetic flux Φd2 The magnetic flux generated by the stator windings interrupts the magnetic flux of the toroidal rotor salient poles, and has an effect in increasing torque and reducing torque ripple.

In the permanent magnet motor described in Patent Document 1, the width of the center salient pole is about 1/3 or more of the circumferential width of at least one pole, and if it is changed to a two-pole 9-groove configuration, only two groove pitches or more are disclosed. As a result of Fig. 7, it is shown that in the above-described conventional configuration, a torque drop occurs.

According to the configuration of the embodiment of the present invention, by maximizing the permanent magnet torque by increasing the area of the permanent magnet and optimizing the width of the three salient poles formed on the surface, it is possible to suppress the occurrence of the central salient pole due to the above-mentioned central salient pole. The d-axis inductance is increased, and by generating a rectifying torque with a good balance of three salient pole widths, the maximum torque generation can be achieved, and the torque ripple is minimized.

Fig. 8 shows the cogging torque tcog with respect to the ratio τcp/τs of the center salient pole width τcp of the permanent magnet and the groove pitch τs. The cogging torque is an index that affects positioning accuracy or noise at low speed. It is understood that the configuration in which the ratio of the rotor magnetic poles to the number of grooves is 2:9 affects the cogging torque in the configuration in which the permanent magnets are arranged as shown in Fig. 1. The cogging torque is a torque chopping caused when the current does not flow through the stator winding. As in the present configuration, in the configuration in which the ratio of the rotor magnetic pole to the number of grooves is 2:9, each magnetic pole pair Holds 18 pulse cycles of the least common multiple of the two.

The magnitude of the cogging effect has a large influence on the magnetic pole width of the rotor surrounded by the permanent magnets 61, 62, 63 (the sum of the salient pole 71 and the salient pole 72 and the pole piece 75), and generally, by Combination special The number of stator grooves of the above-mentioned fractional groove indicates a special generation type. From the results of Fig. 8, it was found that when τcp/τs is 0 or 0.45, it indicates a characteristic having a minimum value. By selecting the above ratio, the cogging torque can be minimized. It has been found that especially when τcp/τs is 0.45, the pulsation torque (torque chopping) is reduced as shown, the torque can be increased, and the cogging torque can also be reduced. If this point is expressed by the ratio of the width between the extremely wide and the permanent magnets, it is 0.7 at the point of τcp/τs = 0 and 0.65 at the point of τcp / τs = 0.45. According to the above configuration, a permanent magnet motor having a small cogging effect can be formed.

1‧‧‧ permanent magnet motor

2‧‧‧stator

3‧‧‧Rotor

4‧‧‧ Stator core

41‧‧‧ trench

42‧‧‧ Stator teeth

43‧‧‧Standard core back

5‧‧‧statar winding (stator winding)

61, 62, 63, 64‧‧‧ permanent magnets

61, 62, 63‧‧‧U-shaped permanent magnets

64‧‧‧Peripheral permanent magnet

7‧‧‧Rotor core

71, 72‧‧‧

73‧‧‧Rotor magnetic circuit

74‧‧‧ center sharp

75‧‧‧Magnetic pole piece

8‧‧‧Rotary axis

9‧‧‧Voids

11‧‧‧Static pin

Τs‧‧‧ trench spacing

Τcp‧‧‧ center width

Τbp‧‧‧ is the width of two salient poles formed between the U-shaped permanent magnet and the peripheral permanent magnet

Τap‧‧‧ contains the total width of the width τbp of the salient pole and the width τcp of the adjacent central salient pole

Claims (6)

A permanent magnet motor comprising a permanent magnet rotor, which is a P-embedded permanent magnet rotor in which a ferrite permanent magnet is housed in a laminated tantalum steel sheet, and is configured by a U-shaped three-pole arrangement. The permanent magnet of the shape and one outer peripheral permanent magnet which is disposed in the circumferential direction of the outer peripheral portion of the U-shaped permanent magnet, thereby generating a permanent magnet torque, and the first pole is formed by the U-shaped Two salient poles between the permanent magnet and the outer peripheral permanent magnet, and one central salient pole formed between the U-shaped permanent magnets adjacent to each other, generating reluctance torque; and the stator a stator winding of a distributed winding and an M phase, and a stator core having a stack of Ns slots accommodating the stator winding, and the ratio of the Ns/M/P is a fraction, and the permanent magnet motor It is characterized in that when the width of the center salient pole is τcp and the groove pitch of the stator core is τs, the width τcp of the center salient pole is made smaller than the groove pitch τs. In the permanent magnet motor according to the first aspect of the invention, wherein the width of the two salient poles formed between the U-shaped permanent magnet and the outer peripheral permanent magnet is τbp, the width of τbp is made wider. The groove pitch τs is small. A permanent magnet motor as recited in claim 2, wherein The width τcp of the center salient pole is set to 0.1<τcp/τs<1.0 with respect to the groove pitch τs. The permanent magnet motor according to claim 3, wherein the width τcp of the center salient pole is set to 0.35 < τcp / τs < 0.7 with respect to the groove pitch τs. The permanent magnet motor according to the second aspect of the invention, wherein the width τbp of the salient pole formed between the U-shaped permanent magnet and the outer peripheral permanent magnet and the width τcp of the center salient pole are included for one pole. The total width τap is set to 2.1 < τap / τs < 3.35 for the groove pitch τs. The permanent magnet motor described in claim 5 is set to 2.57 < τap / τs < 2.84.